The present invention relates to a level detector which is used primarily in a transmitting section or the like of radio communication equipment, for detecting a voltage corresponding to the transmission output so as to suppress its variation by controlling the amplification degree of a transmitting power amplifier. More particularly, the invention pertains to a temperature-compensation typed level detector which is less affected by ambient temperature changes.
In the transmitting power amplifier of the final stage in the transmitting section of radio communication equipment there is provided an automatic output control circuit for holding the transmission output to be substantially constant at all times. That is, when a voltage corresponding or proportional to the transmission output is detected, the detected output is compared with a predetermined reference voltage, and the amplification degree or gain of the power amplifier is controlled so that a difference between the detected output and the reference voltage may be reduced to zero, thereby suppressing variations in the transmission output.
However, prior art has defects such as difficulty in setting an optimum value of the bias voltage of a rectifier, or difficulty in miniaturization.